I generally buy from a national "federated cooperative" (Intermarché) witch despite the claim is a corporate like any others made up by a series of
mostly national producers and a network of supermarket, of course foods have traveled because our actual food system is not much local-centered BUT instead of buy small batch (with packaging and so on) everyday I buy in quantity, store at home. Bread can be freeze issueless, various kind of cheese, not all unfortunately, the same, meat and various sea products equally etc. I drive 20km once a month in mean for groceries. Back in city I've driven 5km every week, notably with
equal travel time due to city traffic.
A set of individual cars is not more efficient than a single truck BUT buying in quantity, with little packaging vs buy small quantity with much more packaging change the number of trucks on the road and the numbers of waste we made, packages are not produced at the supermarket backyard they also need to travel. For instance I tend to buy wines directly from some producers (not all wine I use, but a significant slice, they are between 30 and 45 km) I generally buy in four classic barrels (glass+plastic and glass+straw / wood) bottling in my garage with the same glass bottles every years. Compared to buy single bottles I made FAR LESS traveling because if I buy in bottles they are always new ones, having traveled empty, fill, stickered, traveled again full etc. Similarly for olive oil, I tend to buy it once a year in metal barrels from a relatively near local producer (75km). In the future when I expect far more expensive gasoline prices I'll probably buy an EV recharging it from my present p.v. system, nothing really "ecological" for sure but still cut the need for distributing oils at any station, witch happen with trucks in most cases.
That's not much of a math anyway, the point is that in a distributed economy we tend to produce at a short range, like we have done in the past, surely not all is local, I can't buy local bananas here so to say, but many things can be. For instance why importing Brazilian meat when we have a national production? It's cheaper in the actual system but it should not. Sunflower oil? In a moderately recent past (~20 years) was produced nationally, then Ukrainian/Russians one became a cheaper option for sellers production have shifted. Again we do not need that shift and it was not resulting in lower prices for customers, only bigger margins from sellers. A State-made logistics for national enterprises might be the most efficient answer.